1. Field of the Invention
The field of the present invention is in paving equipment.
2. Related Art
Poured concrete roadways are known to expand and contract in response to seasonal temperature variations. This expansion and contraction will cause uncontrolled cracking in random patterns that will disrupt the surface, provide a rough ride for vehicles traveling over the road and shorten the lifespan of the roadway. The traditional response has been to deliberately cut controlled expansion joints as slots in the roadway slab in order to provide room for expansion in a controlled fashion. These expansion joints in concrete roadways are cut in straight lines, have short metal dowel bars embedded in the concrete underneath them for strength and are typically sealed by a compressible yet waterproof material to keep ice from forming in the cracks. Usually the expansion joints are cut perpendicular to the direction of travel on the roadway, although angled variants are known.
During construction, there are frequent circumstances, for example, hot, windy conditions, when the contractor pouring a new roadway slab faces the possibility of the concrete drying quickly enough that uncontrolled cracking in random patterns on the surface of the slab may begin quickly, sometimes within the space of a few hours. A new slab for a roadway or a runway at an airport having uncontrolled cracking will not meet the specifications of the Department of Transportation or other authority responsible for the new paving. Accordingly, if such uncontrolled cracking appears in newly poured slab, contractor will be required to tear out the slab and start over.
Controlled expansion joint slots are cut into newly poured paving slabs by concrete saws. Concrete saws are comprised of a rotary disk having a cutting edge, a power supply such as an engine to turn the blade and a height adjustment apparatus. Prior art concrete saws, particularly those powerful enough for the paving industry, were heavy, sometimes up to a ton in weight. This weight was supported by wheels, typically four. The wheels on the prior art machines were small metal wheels in order to support the weight of the saw. The small size of the wheels consequently delivered a heavy loading factor to the surface of the slab being cut due to the small area of the wheels touching the slab surface. Accordingly, prior art saws could only work on slabs that were already dry. If the slab was not thoroughly dry, the weight of the concrete saw would cause the saw wheels to sink into the insufficiently dry slab surface, thereby creating unacceptable indentations in it. Hence prior art saws could not be used to cut expansion slots in slabs that were drying too quickly to avoid rapid cracking, because such slabs were still too wet to support the saw's weight.
It is also required that the concrete saws cut the expansion joints in the proper location, and to be as straight as possible. This is done in the prior art by chalk lines. The chalk line was followed by a guide arm on prior art concrete saws that would extend ahead of the rotating blade. A workman would physically move the entire saw as necessary to keep the guide arm on the chalk line. The expansion joint, once cut, was thereafter flushed to remove dust and other debris from it by air pressure, sand blasting or water flushing. The expansion joint was thereafter filled with a material such as silicon and/or caulk to seal it.